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Un cúmulo de hierro y azufre con un centro de hierro de tres coordenadas altamente piramidalizado y una afinidad
Alexandra C Brown1, Daniel L M Suess1
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Journal of the American Chemical Society
|September 1, 2023
Resumen
Los investigadores desarrollaron ligandos de carbenos N-heterocíclicos voluminosos para evitar la agregación de grupos de hierro-azufre, lo que permitió el estudio de grupos reducidos de [Fe4S4]0. El racimo resultante se une al CO, pero muestra una débil afinidad por el N2 debido a la escasa unión Fe-N2.
Área de la Ciencia:
- Química organometálica
- Química bioorgánica
- Química de coordinación
Sus antecedentes:
- Los grupos sintéticos de hierro y azufre son modelos cruciales para las enzimas nitrogenasa.
- La generación de sitios de coordinación abiertos para la unión de N2 a menudo conduce a una oligomerización de clúster no deseada.
- Los ligandos protectores estériles permitieron con éxito la formación de complejos N2 en grupos Mo-Fe-S.
Objetivo del estudio:
- Extender la estrategia de uso de ligandos protectores estériles a los grupos Fe-S exclusivos.
- Para suprimir la oligomerización del racimo durante la reducción de los racimos de Fe-S.
- Caracterizar el producto [Fe4S4]0 reducido e investigar sus capacidades de unión al N2.
Principales métodos:
- Síntesis y reducción de un electrón de grupos de hierro-azufre apoyados por carbenos heterocíclicos (IMes y SIAr).
- Utilizando ligandos SIAr estéricamente exigentes para evitar la oligomerización del racimo.
- Caracterización del cúmulo reducido mediante métodos espectroscópicos y estructurales.
- Investigación de las propiedades de unión de gases (N2 y CO) del grupo Fe-S resultante.
Principales resultados:
- Los ligandos SIAr protectores estériles impidieron con éxito la oligomerización de los grupos de Fe-S tras la reducción.
- La caracterización del grupo reducido [Fe4S4]0, (SIAr) 3Fe4S4, reveló un sitio único de tres coordenadas Fe con una geometría piramidal.
- El grupo (SIAr) 3Fe4S4 se une al CO pero muestra una coordinación mínima de N2, atribuida a un enlace Fe-N2 débil en lugar de un obstáculo estérico.
Conclusiones:
- Los carbenos heterocíclicos estériles voluminosos son efectivos para controlar la reactividad de los grupos de Fe-S.
- El grupo [Fe4S4]0 reducido exhibe un comportamiento de coordinación distinto en comparación con los análogos Mo-Fe-S.
- El débil enlace Fe-N2, no las limitaciones estéricas, explica la baja afinidad por el N2 en estos grupos de solo Fe.
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